1. Field of the Invention
The present invention relates to filtration devices and more especially those to be used for filtering physiological fluids in medical treatments. Its object is to provide a filtration device, the design of which is such that it is, in particular, more suitable than the devices of the prior art, for filtering blood in blood-transfusion installations, e.g. those in operating-rooms.
2. Discussion of the Prior Art
Filters used in installations of that kind should be adapted to be readily and rapidly mounted in the blood-circuit feeding the injection-needle, and they should be of such a low price that they can be disposed of after use. Such filters, however, must allow the user, so long as they are being utilized, to adjust at will the fluid flow-rate within a range that, in some cases, may happen to be very wide. To this end, it is imperative, in particular, to prevent the filter from becoming choked up, which would be likely to obstruct the blood-circulation area within a short time and would unduly reduce the blood flow-rate. Moreover, care must be taken to avoid the penetration of air into the circulating blood, resulting in the injection of air-filled blood into the veins of the patient under treatment.
It is, in fact, the usual practice in blood-transfusion installations, to provide the circuit feeding the injection syringe both with a filter adapted to retain solid materials and with an air-trap for retaining air bubbles. But in such cases, normally two different devices are involved, whereas, in the present invention, the above two functions are combined in a single device, in a single and highly efficient way not only allowing the safe retention of the air-bubbles, but permitting, in addition, the separation of any amount of air contingently mixed with the blood and the retention of same.